This invention relates to the field of perforating-binding or punching-binding machines, for office use, for binding packs of sheets by a comb binder generally made of plastics. Such a type of binder comprises a continuous web and resilient teeth extended tranversely of the web and normally circularly coiled on themselves. First, at a seat thereof, such machines provide for perforating aligned spaced apart holes adjacent one edge of the pack of sheets to be bound together. Then, at a second seat thereof, such machines provide for widening out and momentarily open the comb teeth of the binder, so that the pack of previously perforated sheets can be inserted therebetween, and then release such teeth which close on themselves binding the sheets.
Many of such machines are known and used at present. Generally, they comprise a punching unit and a binding unit on a single frame, generally controlled by means of a single lever. The binding unit comprises two series of finger elements. The elements in the first series are straight and perform the function of holding or retaining the binder web, and the elements in the second series are generally of angled shape or in any case have a portion extended transversely of said first mentioned elements to grip the curl of each resilient tooth of the binder. A relative movement between the two series of finger elements is preset in various known manners.
Generally, the punching unit comprises a series of aligned moving punches, carried by resilient means on a bar fixed to the machine structure or framework, and a movable bar carrying aligned latches, each of which at a position corresponding to a punch, for operating the relative punch upon lowering of the movable bar on the fixed bar. The punches have a lower cutting end cooperating with an opening or die. Generally, the cutting edge of the punch has a single inclination on one side and the opposite side of the punch. Moreover, in order to reduce the strain to be exerted for perforation, the punches are generally of a different length from one another, so that the latches upon lowering of the movable bar would not come simultaneously in contact with all of the punches. Various types of driving units are provided for operation of the punching unit and binding unit. A type of machine widely used at present comprises a rack drive unit.